The present disclosure relates to an image reading device for reading a document image and an image forming apparatus including such an image reading device.
As a reading system of an image reading device, a document fixing reading system is known. In the document fixing reading system, an original document is placed on a contact glass, pressed against the contact glass by a platen mat or the like, and scanned by a reading unit, whereby a document image is read.
As an image reading device employing the document fixing reading system, conventionally, an image reading device explained below is known. In this image reading device, a contact image sensor (CIS) extended in a main scanning direction is arranged below a contact glass as a reading unit. The image sensor is moved in a sub-scanning direction, whereby an original document on the contact glass is two-dimensionally scanned. A guide member extending in the sub-scanning direction is provided on a bottom plate of a housing. A slider is arranged in a lower part of the image sensor. The slider slides along the guide member to move in the sub-scanning direction.
However, in the image reading device, when the bottom plate of the housing is deformed by the influence of heat, the guide member provided on the bottom plate is displaced up and down. When the guide member is displaced up and down, the image sensor guided by the guide member moves up and down. In this case, the distance between the original document on the contact glass and the image sensor changes. Then, an inconvenience occurs in that an image read by the image sensor is defocused and reading quality of a document image is deteriorated. In particular, since the contact image sensor has a narrow focusing range, defocus due to thermal deformation of the housing tends to occur. As a result, the quality of a read image is sometimes substantially deteriorated.
It is an object of the present disclosure to provide an image reading device that can reduce the likelihood that the distance between an image reading section configured to read an image and an original document fluctuates because of the influence of heat and an image forming apparatus including the image reading device.